Switch and signal control system for railroads



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SWITCH AND SIGNAL CONTROL SYSTEM FOR R AILROADS Filed Dec. 13, 1938 9 Sheets-Sheet 8 INVEJIIHORS V 5.N.W|'ghT and AL gdon BY THEIR ATTORNEY Patented Oct. 29, 1940 UNITED STATES SWITCH AN];

Sedgwick N. Wight, Langdon, Brighton,

SIGNAL CONTROL SYSTEM a RAILROADS Rochester, and Andrew N. Y., assignors to General Railway Signal Company, Rochester, N. Y.

I Application December 1 14 Claims.

This invention relates to switch and signal control systems of the entrance-exit type for railways, and more particularly pertains to improvements in such systems as disclosed for example in the applications of A. Langdon, Ser. No. 119,641, filed January 8, 1937, and Ser. No. 176,466, filed November 26, 1937.

In an entrance-exit. type system, the operator may control the power operation of track switches and the clearing of signals of a track layout, so as to provide any desired route for train movement over the track layout, by merely actuating freely movable control buttons or devices to designate the entrance and exit ends of such routes. These control buttons are preferably located on a miniature track diagram representing the actual track layout, at points on the diagram corresponding with the signal locations constituting entrance and exit ends of the routes over the track layout. Generally speaking, such' an entrance-exit type of control system comprises suitable route selecting or establishing means and acts in response to the operation of control buttons to designate the entrance and exit ends of some particular desired route to control the appropriate switches to the positions required to establish that route, and also to effect the clearing of the signal at the entrance to that route when all of the track switches included in such route have properly responded to their control. In a switch and signal control system,'such as disclosed in the above mentioned prior applications and to which the present invention more particularly relates, the operation of the route establishing means; involves a preliminary initiating or conditioning operation in response to the actuation of acontrol button to designate a signal location as an entrance point, and a completion operation in response to the actuation of a control button to designate the exit end of a particular route originating at the designated entrance point.

More specifically, the actuation of a controlbutton to designate any given signal location as an entrance point energizes the initiating circuits and relays for preselecting the positions of certain switches of the track layout as maybe required to conform with all of the various available routes originating at the designated entrance signal location, preparatory to the designation or identification of a particular one of such routes as the desired route. to be established. The energization of appropriate initiating circuits acts to render effective for actuation or manipulation the control buttonior the exit s, 1938, Serial No. 245,384

end of each of the routes originating at thedesignated entrance point only if that route is not 'in conflict with some other established route. There is no power operation of track switches during this preliminary initiating operation; but, when the operator actuates a control button to designate the exit end of a particular one of these available routes originating at the designated entrance signal loc'ation, a completion circuit means is rendered efiective to cause operation of the track switches included in that route to positions required to establish that route by the energization ofv switch control relays in conformity with I the preselecting operation performed by the initiating circuits, and at the time of the'energization'of these switch control relays the respective track switchesare operated, if they are not already in proper positions. The energization of these switch control relays at the same time opens the initiating circuits relating to all other routes originating at the same entrance'signal location. I

A route'establishing means operating in thisv manner. to set up any-desired'route in response to the designation of the entrance and exit end of such route involveaamong other things, a control of the continuity of the initiation circuits by contacts of the switch control relays of switches included in established routes in such away that the initiating circuits relating to 'anyf given switch are not energized a portion of a route or a path for train movement from the designated entrance signal locationto and over that switch in its pre-selected position isin'co1iflict with any route then established, and also 3135 no operating potential is supplied to render the actuation-of a control button efiective to desighate the exit end of a route unless there is some route to that exit end from the designated entrance signal location which is not in a confiict' '40 with any route that may then be established. In other words, the control of the continuity'of the initiating circuits provides in effect an electric interlock between conflicting routes, and also serves to automatically select between alternative or optional routes dependent upon conflict of any established route with the respective alternative routes, in a manner shown and described more in detail in the above-mentioned prior application Ser, No. 176,466, filed November 26,50 1937.

Another characteristic of the embodiment of the present invention is that the switchcontrol relays,=which govern the continuity of the initiating circuits and thus determine when a route or portion thereof is in conflict with some route then established, are maintained energized by the presence of a train in the route, so that the interlock between conflicting routes and the automatic selection of optional routes is eifective while a route is occupied by a train, as well as While a route is established by the route establishing means. In this. connection, since the control buttons of the system are freely movable and might be manipulated to exercise a control to change the position of the switch in a route under or ahead of a train, the system includes route locking means of some suitable form to lock each switch in a route against power operation while a. train is approaching or passing over that switch; and in the preferred embodiment of the invention illustrated, this same route locking means is employed to maintain the energization of the switch control relays, as by closing a stick circuit therefor, until the train entering a route has passed over the corresponding switch.

The system embodying the present invention also provides that the buttons operated to designate entrance signal locations, as well as the buttons for designating exit ends of routes, are of the self-restoring push button type and are automatically restored to a normal inactive condition after each manual actuation. The momentary actuation of an entrance push button is arranged to energize a stick relay, conveniently termed an entrance relay, which is maintained energized by its stick circuit until a train passes the corresponding signal location, whereupon the entrance relay is automatically deenergized with the same effect as when an entrance button of the stay-where-put type is manually restored upon passage of the train as disclosed in the above mentioned prior application Ser. No. 119,641. The stick circuit for the entrance relay is also arranged to be openedby manually operable contact means, preferably associated with the same button, so that the entrance relay may be manually restored to normal, whenever the operator so desires, as in the event a route is established prematurely or by mistake. In the specific arrangement illustrated, provision is made to open the stick circuit of an entrance relay only momentarily when a train passes the corresponding signal, so that the entrance relay can again be energized if desired by subsequent actuation of the button while a train is still present and thereby clear a signal for a following train to enter the occupied route, but this specific feature of control is optional and may be omitted Where it is not desired to clear signals for train movement into occupied routes.

This invention also relates to What is termed through route control for a plurality of so-called interlocked groups. An interlocked group in this sense may be said to comprise a group of switches adapted to provide in their difierent positions certain routes between entrance and exit points, each of these routes conflicting with one or more others, and requiring some form of interlocking control toprevent conflicting routes being set up at the same time. An interlocked group may comprise, for example, two or more parallel tracks interconnected by one or more-crossovers, with some or all of the parallel tracks also connected by one or more single switches to branch tracks or sidings.

When the track layout includes two or more such interlocked groups, there may be certain routes of these interlocked groups which may be set up at the same time m end-to-end relation,

so to speak, and provide a through route over two or more successive interlocked groups past one or more entrance signals for these routes which constitute in effect intermediate signals in the through route. Although these routes in end-to-end relation may be established for each interlocked group individually by entrance-exit control, it is desirable for various reasons to provide a through route control of the route establishing means of the respective interlocked groups in such a way that any through route may be established and the intermediate. signals cleared merely by the actuation of buttons to designate the extreme entrance and exit ends of that through route, and without requiring manipulation of buttons for the intermediate signal locations.

A system involving a preselectiton and a completion operation in the manner above briefly explained and disclosed in the prior application Ser. No. 119,641, is well adapted for this desired through route control, particularly in connection with the automatic selection of only one of the different alternative through routes that the track layout may afford. Generally speaking, in order to provide the desired through route control, electrical connections for through route operation are provided for each signal, which may become an intermediate signal in some through route, for interconnecting the initiating circuits for adjoining interlocked groups with respect to these signals, so that the operation of a button to designate any entrance signal location is effective to energize the initiating circuits of all interlocked groups as may be required to conform with all of the through routes originating at that entrance signal location, as well as the routes over the interlocked group with which said entrance signal location is associated.

In other words, the initiating and preselecting effect is extended over successive interlocked groups preparatory to establishing routes in endto-end relation over these interlocked group as may be required, and this preselecting action is dependent upon the availability of routes or portions thereof with respect to the interlocked groups as a whole in the same manner characteristic of a single interlocked group, so as to select automatically alternative through routes and render effective the operation of buttons to designate the exit ends of only those through routes available. After such preliminary initiating or preselecting operation, if the exit end of a through route is designated by the manual actuation of a button, the switches in the remote interlocked group are operated by the completion .circuit means in accordance with the preselection to set up a route over that interlocked group connecting with a particular entrance signal thereof, and suitable relay means at that entrance signal is automatically energized by the completion circuit means to perform entrance and exit functions for that signallocation so as to clear the corresponding signal and control the completion circuit means of the adjoining interlocked group in the same way as if buttons had been manipulated to designate that signal location as the entrance end of a route through the remote interlocked group and the exit end of a route connecting therewith through the adjoining interlocked group, the same operation being repeated for as many interlocked groups as may be involved.

In accordance with one feature of the improvement constitutingthis invention, when a; portion of a through route'is completed through an interlocked group, a through route relay for the corresponding intermediate signal location is energized by the completion circuits and acts to energize automatically the entrance relay for that signal and also exercise an exit control'for the completion circuit means of the adjoining interlocked groups, this control exercised by said through route relay being effective only temporarily, so as not to interfere with the subsequent restoration of the entrance relay, or the proper operation of the route establishing means of the adjoining interlocked group by reason of any maintained exit control performed by the through route relay.

In connection with this through route control, there are various conditions under which the through route connections for the initiating circuits of the adjoining interlocked groups should be broken to prevent interference with the regular operation of setting up routes through different interlocked groups, and to avoid improper control of switches and signals by through route control under certain conditions. In the first place, the through route connections for each intermediate signal are opened when the. corresponding signal is either the entrance or the exit end of an established route. In the arrangement of circuits illustrated, the through -route connection for each intermediate signal includes back contacts of the corresponding entrance relay and exit relay.

Another feature is that the through route connections for each intermediate signal are broken by suitable track circuit controlled means whenever a route terminating at that signal is occupied by a train irrespective of the direction of movement of the train when entering said route.

In the-specific embodiment of the invention illustrated, this desired control of the through route connections is accomplished by including in said connections associated with an intermediate signal the front contact of the track relay 0r relays for the track section or sections in any possible route extending to that signal, these track relay contacts serving to interrupt the through route connections when a train is present regardless of the direction in whichthe train entered the corresponding track section.

Considering a further feature of the control of the through route circuit connections, when a train traverses a through route, the intermediate signals are automatically caused to assume the stop condition as the train passes each signal by the automatic deenergization of the corresponding entrance relay; and in connection with this automatic restoration, provision is made in accordance with this invention so that the through route connections for an intermediate signal are not closed when a train passes that signal until the routeestablishing means for the route originating at that signal is effectively de energized. This route establishing means includes among other things an exit stick relay or equivalent; and if the through route connections were not thus kept open, this relay might be maintained energized improperly, if the train should happen to pass the intermediatev signal and deenergize its entrance relay at the time the initiating circuits for the adjoining interlocked group had been energized by the operation of some entrance button. In the specific embodiment of the invention illustrated, each of the through route connections are controlled by the front contact of a relay M which is closed only when the corresponding signal has assumed its stop condition; and when an entrance relay is deenergized by a passing train, this relay acts to keep open thethrough route connections temporarily until the signal has assumed its stop condition, and long enough for the exit stick relay to be effectively deenergized and cause the completion circuit means to assume its normal condition.

Another feature of the through route control characterizing this invention is that through routes may not be established to allow a train to move from the track layout under the operators control into a stretch of track in a direction opposite to the direction of traific for which this stretch of track is normally used. It is contemplated that the through route control will be shunting train movements; and it is considered desirable that such through route control should not be used by the operator carelessly or accidentally to direct a train into a stretch of track against the normal direction of trafiic. The operator may establish a route through an interlocked group into an adjoining stretch of track against the normal direction of traffic by manipulation of the entrance and exit control buttons for that particular interlocked group, when a shunting train movement or other condition may require, but cannot do so by through route control. Generally speaking, in accordance with this invention, an extra selector relay is employed, which is responsive to the energization of initiating circuits by the through route connections, but not by the operation of the corresponding entrance button, to interrupt the appropriate initiating circuits and render ineffective the manual actuation of a button to designate the exit end of a through route which would direct a train into a stretch of track against the normal direction of 'traffic.

Another feature of the present invention relates to the automatic selection of optional or alternative routes that may be afforded by the track layout. In the type of system disclosed in the prior application Ser. No. 176,466 above mentioned, optional routes are automaticall selected by preselecting the position of each trailed crossover switch, or crossover required to be in different positions for the optional routes for operation by the completion circuit means to the normal position in preference to the reverse position, with the result that the preferred optional route is that one over the remote crossover or crossovers in the normal position and the crossover nearest the entrance signal in the reverse position.

Under certain special conditions, however, it may be desirable to have the preferred optional route, which is established unless some conflict exists, include the remote crossover in the reverse position instead of the normal position. For example, the remote crossover may be more suitable for train movement at high speed than the near crossover, or perhaps it may be expedient to use the remote crossover in its reverse position for the preferred optional route so that trains may be brought to acertain platform or other track location. In View of these continprovides means by which the preferred or superior optional route ordinarily obtained is over the remote crossover in the reverse position, rather than the normal position. In one arrangement, the preselecting or route selector relay for this remote crossover is arranged to be energized by initiating circuits corresponding to the reverse position of this crossover, and to act when energized to cause this crossover to be operated to the reverse position by the completion circuit means. According to another arrangement, the initiating circuit for preselecting the normal position of the remote crossover is normally kept open by a special selector relay, and is not closed unless one end of this crossover in the normal position is included in some established route, so that this crossover cannot be used in the reverse position for the superior optional route.

A still further feature of this invention relates to the provision of an electric interlock between the exit relays of adjoining interlocked groups, so that two routes over these interlocked groups cannot be set up contemporaneously toward the same signal location constituting the common exit end of these routes. This serves as a check upon the manipulation of the buttons by the operator, so that he will not carelessly or accidentally establish routes at the same time to bring opposing trains up to the same signal location. Also, the entrance relays for the same signal location and adjoining interlocked groups are provided with electric interlocking circuits as a further check upon the operators manipulation of the control buttons.

Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawings, and in part pointed out as the description of the inven tion progresses.

In describing the invention in detail, reference will be made to the accompanying drawings, in which like reference characters designate corresponding parts throughout the several illustrations, similar letter reference characters being used to designate parts of a similar nature which are generally made distinctive by preceding numerals, and in which:

Figs. 1A, 1B and 10, when placed end-.to-end above Figs. 1D, 1E and IF respectively, illustrate the self-selecting network provided for this particular embodiment of the present invention;

Fig. 2 illustrates certain typical circuits relative tothe track switch and signal controls; and

Figs. 3A and 313, when placed end-to-end, illustrate the track layout and signal controls for this embodiment of the present invention.

In considering various parts of a similar nature from time to time during the disclosure, reference is made in a general manner to those parts by letter reference characters without their preceding numerals. It is to be understood that such a reference applies to any parts designated in the drawings by reference characters that are similar except for numerals associated therewith.

The various parts and circuits constituting the embodiment of the present invention have been shown diagrammatically and certain conventional illustrations have been employed for the purpose of simplifying the illustration and facilitating in the explanation of the invention. The drawings are made more for the purpose of facilitating the disclosure of the invention as to the principles involved and the mode of operation, than for the purpose of illustrating the specific construction and arrangement of parts that would be employed in practice. Thus, thevarious relays and their contacts together with control buttons and other apparatus are illustrated in a conventional manner, and symbols are used to indicate connections to the terminals of batteries or other sources of electric current instead of showing all of the wiring connections to those terminals.

The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries, or other sources of direct current; and the circuits with which those symbols are used always have current flowing in the same direction. If alternating current is used instead of direct current, the symbols should be considered to represent the instantaneous relative polarities applied to the circuits. It is to be understood that certain of the various circuits can be energized from a common battery and that several batteries can be provided where required in practice. I

To facilitate in the disclosure of the present invention, various relays and circuits are shown in duplicate on various pages of the drawings, and those relays and circuits shown having corresponding reference characters are to be cons dered identical.

Apparatus Track layout-With reference to Figs. 3A and 3B, two parallel tracks have been illustrated as connected together at various points by crossovers having track switches 2TSA, ZTSB, 3TSA, 3TSB, 4TSA and 4TSB.

'I'hese parallel tracks with connecting crossovers and associated signals constitute two interlocked'groups. One of these interlocked groups includes the crossovers 2 and S for providing routes between the signals [0 and H at one end of the interlocked group and the signals 52 and I3 at'the other end of the interlocked group; and the interlocked group comprises the crossover 4 to provide routes between signals is, l5, l6 and I1. It will be noted that the crossovers 3 and 4 are so disposed as to provide alternative or optional through routes between the signals ill and I1, this arrangement being shown to illustrate how the principles of this invention may be employed to select a superior or preferred optional through route. It should be understood that this invention is applicable to various arrangements of single tracks, switches, crossovers, and the like, of any conventional track layout; and the track layout shown represents merely one simple arrangement to illustrate the nature of the invention.

The track switches are positioned by power operated switch machines which can be of any suitable type such, for example, as the switch machine shown in the patent to W. K. Howe, Patent No. 1,466,903, dated September 4, 1923. The motors of the switch machines can be controlled in any suitable manner, such, for example, as in the patent to W. H. Hoppe, et al., Patent No. 1,877,876, dated SeptemberZO, 1932. If the switch machine motors are controlled in accordance with that Hoppe et al. patent, the relay OR of that patent is controlled by the relay WZ illustrated in Fig. 2 of the present disclosure.

In order to simplify the present disclosure only one switch machine SM has been shown for each crossover, because the track switchesfor both ends of the crossovers should usually assume corresponding positions. Thus, switch machine ZSM has been provided for positioning track switches 2TSA and ZTSB, switch machine ilSM has been providedfor positioning track switches 3TSA and STS'B- and switclri-machine ISM has been provided for positioning trackswitches 4-ISA and 4TSB. It is to beunderstood that a separate switch machine SM can be provided for governing each track switchin accordance with the requirements of practice.

A polar neutral relay WP is provided for each crossover for repeating the locked position of the track switches in correspondencewith the locked position of the switch machine. That is, relay ZWP, for example, is energized with one polarity when the switch machine 2SM is in a normal locked position and the track switches ZTSA and ZTSB are looked normal, and that relay is energized with the opposite polarity when switch machine ZSM is in a reverse locked position and track switches ZTSA and 2TSB are locked reverse. Relay 2WP is dropped away whenever either of the two above conditions are not completely satisfied. The control circuits for the relays WP are selected to provide such a mode of operation by point detector contact mechanisms such as the type shown, for example, in the patent to C. S. Bushnell, Patent No. 1,517,236, dated November 25, 1924.

Signals I0, iI, i l and I5 have been provided for governing east bound tra'fiio, to the right, and signals I2, it, It and I 1 have been provided for governing west bound traffio, to the left.

The signals have been illustrated as being of the search light type. The search light type signals can be of a type such as is shown, for example, in the patent .to O. S. Field, Patent No. 1,835,150, dated December 12, 1931. Each of the signals illustrated in this disclosure is provide-d with contacts closed only when the signal is at stop, as shown in that Field patent, for energizing a signal at stop repeater relay M associated with that signal. The signals are considered to provide a normal-at-stop red indication and a clear green indication. It is also to be understood that a yellow indication for caution can be provided if such indication is required in practice, and that other types of signals could as well be employed in accordance with the present invention,

such, for example, as signals having individual color lamp units or signals of the semaphore The track layout has been divided into track sections by the usual insulated joints to provide the usual track circuits tor the track relays. Track sections 6, i, 8 and 9 have been shown as having associated therewith track relays 6T, 1T, dT and 9T respectively. Slow acting track repeater relays BTP, FTP, 8TB and 9TP are'provided for track relays 6T, IT, ST and ST respectively. It is of course to be understood that the number of track circuits can be varied in accordance with the requirements in practice from the particular track circuit arrangement illustrated in the present disclosure. The track circuits are assumed to be of the usual normally energized type, and the track switches are assumed to be properly bonded to provide fouling protection, all of which details have not been shown in order to simplify the present disclosure, because those details are well known to those familiar with the art.

Control machine.-The control machine provided for governing traffic through the track layout heretofore described, has a control panel upon which is constructed a miniature track diagram (see Figs. 1A, 1B and 10) corresponding .to that track layout. The miniature track diagram is provided Withsuitable indication means along exit points inthe track layout.

the diagram sections representative of the track sections and track switches to provide necessary indications with respect to routes that have been established, the presence of trains on the sections, and the indication of the signals at the various points in the track layout. Inasmuch as this in- Vention'relates more particularly to the use of a self-selecting network in setting up the various routes,'those indications have not been shown. Such indications can be provided as shown and described in the prior Hitchcock application, Ser. No. 74,709, filed April 16, 1936, and in the prior Langdonapplication, Ser. No. 176,466, filed No vember 26, 1937.

An entrance button NB is provided on the miniature track diagram for the entrance point to each route as defined at the track layout by the location of the signals. Thus, buttons IONB, IINB, I2NB, I3NB, I lNB, I5NB, IGNB and I'INB have been provided on the control panel as representative of entrance points at signals Iii, II, I2,

. I3, I4, I5, I6 and I! respectively. The buttons are located on the miniature track diagram at positions corresponding to the positions of the signalsat the track layout for governing entrance at those entrance points. Eachentrance button NB is of the push-pull button type. That is, the button is biased to a normal position from which it can either be depressed or pulled out. There is an operating contact on the button which is closed when the button is depressed, and there is a normally closed contact on the button which is closed when the button is in its normal position as well as when it is depressed. When the button -is pulled out, the normally closed contact isopened. The construction and contact arrangement for such a push buttoncan be provided, for example, as shown in the application of J. F. Merkel, Ser. No. 158,720, filed August 12, 1937.

An exit button X8 is provided for. the exit end of each possible route in the track layout, and

.the exit buttons are located on the track diagram at positions corresponding to the actual Exit buttons IUXB, IIXB, IZXB, I3XB, MXB, IBXB, ItXB and I'IXB are provided for exit points at signals I0, II, I2, I3 I4, I5, I6 and I! respectively. The exit buttons XB are of the self-restoring push button type, each'having a contact closed only when that button is depressed.

Although separate push-buttons illustrated for each entrance and exit point associated'with each signal, it is to be understood that other forms of control switches could as well be used for those points, and that the entrance and exit buttons for each signal location could as well be combined into a single control switch having distinctive positions to provide the selection of the circuits necessary in accordance with the present invention. It is also to be understood that the distinctive entrance and exit control contacts can be included on one push button with circuit means-provided for distinction such asis shown, for example, in the Preston application Ser. No. 183,499, filed January 5, 1938.

A switch control lever SML is. provided on the control panel for eachcrossover, as is typically shownin Fig. 2 for governing track switches ITSA andATSB, the, leveriiSML having anormal center position, a left hand position for operating the associated track switches to a normal position, and a right hand position for have been] operating. the .associated track switches .to..a..r,e

verse position. Contacts are provided on the lever for each of those positions.

System devices.With reference to Figs. 1A, 1B, 1C, 1D 1E and IF, each or the entrance buttons NB has associated therewith an entrance or repeater relay NR which is picked in response to the depression of that entrance button, and maintained energized dependent upon the passage of a train, or the actuation of a button for manual restoration to normal.

An exit relay 3m is provided for each exit point in the track layout, and that exit relay is picked up when a route is set up having an exit point with which that relay is associated. Each relay XR is maintained picked up dependent upon the entrance relay NR for the route with which that exit point is associated.

A relay AY or BY is provided for each of the track switches for initially selecting the position of that track switch in accordance with the defining of each entrance point by the depression of an entrance button. Relays ZAY, 3AY and 4AY have been illustrated as being associated with track switches Z'ISA, 3TSA and ATSA respectively, and relays ZBY 3BY and 531 have been illustrated as having been associated with track switches 2TSB, 3TSB and, dTSB respec tively. Special route selector relays BYY and 4YY have been provided for governing the control circuits of certain of the Y relays.

The relays AN, BN and R are provided for causing the operation of the track switches in accordance with routes defined by an operator by the operation'of buttons for entrance and exit points. Relays ZAN, 3AN and QAN are pro vided for causing the operation of the track switches of crossovers 2ts, 373s and tits to a normal position in accordance with the setting up of routes including that position for the track switches ETSA, STSA and iTSA respectively. Relays ZBN, 3BN and 4BN are pro-vided for causing the operation of the track switches for the crossovers Zts, 3ts and 4258 respectively, to a normal position in accordance with the setting up of routes including that position for track switches ZTSB, 3TSB and 4TSB respectively. Relays 2R, 3R and 4R are provided for causing the operation of the track switches for crossovers 2ts, 3ts and Ms respectively to reverse positions. The relays AN, BN and R are picked up, in accordance with pick up circuits selected by the Y relays, upon the designation of an exit point during the setting up of a route.

A slow release relay XP is associated with the entrance and exit relays through route control provided for each intermediate signal for the purpose of setting up routes initiated by end-toend control.

Each of the detector track sections is provided with a normally energized lock relay L as is typically shown in Fig. 2 of the accompanying drawings, relays 8L and 9L having been provided for the detector track sections associated with track switches 4TSA and 4TSB. The control circuits for the relays L have been shown as including contacts of route locking relays ES and WS which are provided for the various track sections in accordance with the requirements of practice. Inasmuch as it is contemplated that such route locking relays ES and WS be controlled as shown in prior applications, the circuits for those relays have not been shown as reference can be made to other applications for the manner in which they are controlled, such as the prior application of A. Langdon, Ser. No. 176,466, filed November 26, 1937. If approach locking is to be used as well as route locking the relays ES and WS can be controlled in a manner similar to that shown for relays bearing similar letter reference characters in the patent to C. F. Stoltz, Patent No. 2,115,511, dated April 26, 1938. It is to be understood that other forms of route and approach locking can as well be used with the entrance-exit system provided by the present invention.

A normally energized lock repeater relay LS is provided for each crossover as is typically shown in Fig. 2 of the accompanying drawings, in which relay 4LS is shown as a repeater of the relays L provided for that crossover.

A polar neutral switch control relay WZ is provided for controlling the switch machines for each crossover in accordance with the position of the switch control relays AN, BN and R for that particular crossover. Inasmuch as each relay WZ has a similar mode of operation, only the detail circuits for relay 4WZ has been shown, those circuits being typical of the circuits provided for the relays WZ associated with the other crossovers included in the track layout.

Correspondence relays NCR and RCR are provided for each crossover for repeating the position of the track switches in correspondence with the position of the relays AN, BN and R for those track switches. Relays 4NCR and 4RCR have been shown as typical of the correspondence relays provided for each of the crossovers.

A signal control relay G (see Figs. 3A and 3B) is provided for governing each signal, each relay G being energized only when a route has been completely established having that signal as an entrance point.

Having thus considered the apparatus provided in accordance with the present invention,

the mode of operation of the system is herein-.

after disclosed more in detail in considering various typical operations of the system.

Operation Normal conditions.-The normal conditions of the system are considered as those conditions which exist when the track sections illustrated are unoccupied, the signals are all at stop, and when there are .no entrance or exit points defined by the operation of buttons for those points. An operator is informed of such normal conditions by the various indicator lamps (not shown) which are extinguished under such conditions to provide a normally dark board with respect to the illumination of the indicator lamps.

Under normal conditions the track switches are in their last operated positions, which, for illustration of the present disclosure, has been assumed to be the positions providing through routes on each of the parallel tracks.

Of the relays associated with the self-selecting network, only the special route selector relay 3YY is normally energized. The circuit by which relay 3YY (see Fig. 1B) is energized is closed from through a circuit including back contact 20 of relay 4AN (see Fig. 1C), wire 82, contact 2| of button I3XB closed in a normal position,

back contact 22 of relay I3XR, back contact 23 of relay 3R, and winding of relay 3XY, to

The lock relays L are normally energized as is typically shown for relays 8L and 9L (see Fig. 2). A circuit is closed for the energization of relay 8L from through a circuit including front contact 24 of relay 8T, front contact 22l of relay 8E8, front contact 222. of relay 8W8,

winding of relay 8L, and front contact 25 of relay 8L, to A circuit for maintaining relay 9L picked up under normal conditions is closed from through a circuit including front contact 25 of relay 9T, front .contact 223 of relay 9E3, front contact 224 of relay QWS, winding of relay 9L, and front contact 2! of relay 9L, to

With the lock relays L in a picked up position, a circuit is closed, under normal conditions, for each of the lock repeater relays LS, as is typically shown by the circuit for relay 4LS closed from through a circuit including front contact 28 of relay 8L, front contact 29 of relay 3L, back contact 30 of relay 4W2, and winding of relay ALS, to

In accordance with the last operated positions of the track switches, as illustrated in Figs. 3A and 3B, the correspondence relay NCR for each of the crossovers is normally energized as is typically shown for relay 4NCR (see Fig. 2). Relay iNCR is energized under such conditions by a circuit closed from through a .circuit including back contact 3| of relay 4R, winding of relay ANCR, polar contact 32 of relay 4W? in a right hand position, and front contact 33 of relay AWP, to

The signal repeater relay M provided for each signal is normally energized by a circuit similar to the circuit typically shown for relay I5M.

Relay IEM is normally energized by a circuit closed from througha circuit including contact 34 of signal l5 at stop and winding of relay l5M, to

Initiating and completion circuits.-As already generally outlined and explained more in detail in the prior application Ser. No. 119,641, the operation of establishing a route in accordance with the mode of operation characterizing this invention involves the energization of initiating circuits in response to the actuation of any given entrance button to preselect the position of trailed switches included in all of the various routes originating at the corresponding entrance signal location, and also to supply an operating potential to the exit relays for the exit ends of all of these routes then available. In the specific arrangement illustrated, these initiating circuits are arranged in the form of a network, one for each direction of train movement; and the circuit branches of the network are arranged to control the energization of preselecting or route selector relays AY and BY associated with the switches at the ends of the crossovers. The energized or deenergized condition of these route selector relays determines the position to which the corresponding switch is operated by the completion circuit means. With the exception of certain route selector relays specially controlled for optional route selection in a manner later explained, each route selector relay is energized when the corresponding switch is trailed in a normal position in some route originating at the entrance signal location designated by the manual actuation of an entrance button,-

the route selector relay for a switch trailed in the reverse position being left deenergized, and the route selector relay for a facing point switch being unaffected.

After such an initiating or conditioning operation as a result of the energization of the appropriate route selector relays, the manual actuation of an exit button for a particular one of the available routes originating at the designated entrance signallocation acts to energize an exit relay,. which supplies, current to completion cir.-.

cuits to cause energization of the appropriate switch control relays of the switches involved in this particular route, this energization of the switch control relays acting to open the initiating circuits relating to all other routes originating at the same entrance signal location.

To consider an example of how a route is set up within an interlocked group, assume an operator, after checking his indicator lamps to find that the proposed route is available, depresses entrance button MNB. The depression of button MNB causes the picking up of relay MNR by closing a circuit from through a circuit including contact 35 of button MNB closed in a depressed position, wire 83, back contact 36 of relay IZNR, wire 84, front contact 31 of relay ST, and winding of relay MNR, to The picking up of relay MNR closes a stick circuit for maintaining that relay picked up from through a circuit including contact 35 of button i l-NB closed in both a depressed and a normal position, front contact 38 of relay MNR, wire 33, back contact 36 of relay lZNR, wire 84, front contact 31 of relay ST, and winding of relay MNR, to In each of the above described circuits, back contact 2M of relay BTP is connected in the circuit in multiple with front contact 3'! of relay 8T to provide that the circuits can be closed again immediately upon entrance of a train into track section 8 if it is desired to set up a route at that time for a following train.

It is to be understood that the back contacts of the track repeater relays TP, connected in multiple with the front contacts of the track relays T in the stick circuits for the entrance relays NR, can be eliminated in conditions encountered in practice where it is not required that an operator be permitted to set up a route for a following train when the preceding'tra-in is occupying the track section immediately beyond the entering signal to that route.

The energization of the entrance relay MNR, and the closing of its contact 39 supplies current to the appropriate initiating circuits which function is to preselect the position of the trailed switches included in the various routes originat ing at this entrance signal location. In the example under consideration, where the entrance relay HlNR is energized, the only switch in a trailing relation to the corresponding entrance signal i4 is the lower end of the cross-over 4, and since this switch is' trailed in the reverse position, no route selector relay is energized.

The initiating circuits also'supply an operating potential to the exit relays of the various available routes originating at a designated entrance point. In the case under consideration, operating potential is supplied to the exit relay HXR over an initiating circuit from front contact 39 of entrance relay MNR, back contact 40 of relay MXR, back contact M of switch control relay l lAN, back contact 42 of switch control relay QBN, contact 33 of route selector 41332,

to one terminal of the winding of the relay l'lXEt. This initiating circuit includes back contacts M and 42 of the switch control relays AAN and GBN, so that if a route over either end of the crossover A in the normal position is established, such routes being necessarily in conflict with any route between the signals M and H, the initiating circuit just traced is open, and any operation of the exit button- HXB is not effective to energize the exit relay HXR. There'is a similar: initiating circuit for supplying an operating potential to the exit relay IEXR through .the back contact 2I2 of the special selector relay lYY, for reasons later explained, back contact 2I3 of switch control relay 4BR to one terminal of the exit relay IGXR. This initiating circuit,

for a route from signal I4 to signal I6 over the upper end of the crossover '4 in the normal position is broken by the contact 2I3 if the switch control relay 4R is energized for any conflicting route over the crossover 4 in the reversed position.

Assuming that the operator selects the signal I! as the exit end of the desired route and operates the exit button IIXB, the exit relay is energized by the flow of current over the initiating circuit above traced through the back contact 44 of the entrance relay I'INR, contact 45 of exit button I'IXB, to This energization of the exit relay IIXR closes its contact 46 to provide a shunt for the contact of the exit button, so that the exit relay is maintained energized after the exit button is released and restored to its normal position.

This energization of an exit relay supplies energy to a completion circuit network to energize the appropriate switch control relays to establish the desired route. In the example under consideration, upon energization of the exit relay I 'IXR, the reverse switch control relay 4R (see Fig. 1F) is picked up when its circuit is closed from through a circuit including front contact 41 of relay I'IXR, back contact 48 of relay 4BY, upper winding of relay 4R, back contact 49 of relay 4BN, and back contact 50 of relay 4AN, to The picking up of relay 4R causes the operation of the track switches 4TSA and 4TSB to a reverse position in a manner hereinafter described when considering further details of the control for the track switches.

To consider another example of how the setting up of routes is accomplished within an interlocked group, assume an operator performs manipulations to set up a route from signal I to signal I! when that route is available, and the system is initially under the normal conditions shown and described.

In response to the depression of button I5NB (see Fig. 1C), relay ISNR. is picked up when a circuit is closed of a similar character to that circuit described for the picking up of relay I4NR. Relay I5NR, when picked up, is maintained picked up by a circuit similar to the stick circuit described in detail for relay I 4NR.

The picking up of relay I5NR, under such conditions, causes the picking up of relay 4BY when a circuit for that relay is closed from through a circuit including front contact 5I of relay I5NR, back contact 52 of relay I5XR, back contact 53 of relay 4R, and winding of relay 4BY, to

The picking up of relay 4BY allows the picking up of relay IIXR when its circuit is closed upon the depression of the exit button I 1253 by an operator, from through a circuit including front contact 5I of relay I5NR, back contact 52 of relay I5XR, back contact 53 of relay 4R, front contact 43 of relay 4BY, winding of relay I'IXR, back contact 44 of relay I'INR, and contact 45 of button I'IXB closed in a depressed position, to The closing of front contact 46 of relay I'IXR. provides stick energy for the circuit just described to maintain relay I'IXR picked up after button I'IXB is restored to normal.

When relay I'IXR is picked up, after entrance and exit points have been defined by the operator as being at signals I5 and II respectively,

a pick up circuit is closed for relay 4BN (see Fig. 1F) from through a circuit including front contact 41 of relay IIXR, front contact 48 of relay 4BY, upper winding of relay 4BN, and back contact 54 of relay 4R, to

By describing the mode of operation of the self-selecting network for setting up a route over crossover 4ts requiring its track switches in a reverse position, and by describing the mode of operation in setting up a route requiring track switch 4TSB to be normal, the use of the route selector relay 4BY to select between relays 4R and 4BN has been illustrated; that is, relay 4R is energized when relay I'IXR is picked up if relay 4BY is in a dropped away position, and relay 4BN is energized when relay IIXR is picked up if relay 4BY is in a picked up position. Such mode of operation is characteristic of this entrance-exit system, irrespective of the number of track switches included in each route to be set up.

Switch controls-After considering the mode of operation of the system for setting up routes within an interlocked group, consideration is now given to the means provided for controlling the track switches in accordance with the picking up of the switch control network relays AN, BN and R, and in accordance with the operation of an auxiliary switch control lever SML provided for each crossover. Inasmuch as the track switches for each crossover are controlled in a similar manner, many of the details for the switch control have been shown only for crossover 4ts. It is to be understood that the circuits shown for crossover 4ts are typical of the circuits provided for governing the track switches for each of the other crossovers included in the track layout, and it is also to be understood that similar circuits are provided in practice, as required, for governing single track switches.

With reference to Fig. 2, assume relay 4R to be. picked up in setting up a route as heretofore described, for example, from signal I4 to signal II. The picking up of relay 4R, with relay 8L, 9L and 4LS picked up as described when considering the assumed normal conditions, closes a circuit for the energization of the lower winding of relay 4WZ from through a circuit including front contact 28 of relay 8L, front contact 29 of relay 9L, front contact 55 of relay 5R, and lower winding of relay 4WZ, to The picking u of relay 4WZ, due to such energization, causes the operation of the polar contacts for that relay to a left hand position, and the energization of the switch machine 4SM to operate the associated track switches to a reverse position. Such energization is effected upon the closing of an obvious circuit including front contacts 56 and 51 of relay 4WZ.

The picking up of relay 4B, in getting up the assumed route, causes the dropping away of relay 4NCR by opening its circuit at back contact 3|, thus relay ILS is maintained picked up after relay 4WZ is picked up to open its pick up circuit at back contact 30, by a circuit closed from through a circuit including front contact 28 of relay 8L, front contact 29 of relay 9L, back contact 58 of relay 4RCR, back contact 59 of re-' lay 4NCR, front contact 60 of relay 4LS, and winding of relay 4LS, to

As soon as the track switches 4TSA and 4TSB have been locked in their reverse positions in setting up a route from signal I4 to signal I1, the relay 4WP is picked up when energized with a polarity to operate its polar. contacts to a left hand position, and the picking up of that relay closes a circuit for relay 4RCR, from through a circuit including back contact 6| of relay AAN, back contact 62 of relay SBN, winding of relay 4RCR, polar contact.32 of relay 4W in a left hand position, and front contact 33 of'relay AWP, to The picking up of relay ARCR, due to such energization, causes the dropping away of relay 4L8 by openingits stick circuit at back contact 58. The dropping away of relay 4LS closes the signal control circuit for signal M as is hereinafter described in considering'the detail of the signal control circuits. When relay 4W? is dropped away assoon a either of the track switches ATS A and 4TSB' have been unlocked from their normal position, a stick circuit is closed for relay 4WZ from through a circuit including back contact 63 of relay lWP, front contact 64 of relay 4W2, polar contacttS of relay AWZ, in a left hand position, and lower windingof relay 4WZ, t0

, Such stick circuit provides that relay. 4W2 is maintained picked up to complete the operation of the switch machine, irrespective of the dropping away of relay 4R, incase an operator cancels the proposed route before the switch machine 48M has completed its operation.

A similar mode of operation is effected when the track switches are operated from a reverse to a normal position. For example, assume a route to be initiated from signal 15 to signal I! when the normal conditions of the system exist as described. The picking up of relay dBNin setting up such a route in a manner heretofore described, causes the pickingup of relay lWZ when a circuit is closed for the upper winding of that relay from through a circuit including front contact 28 of relay 8L, front contact 29 of relay 9L, front contact 61 of relay BN, and upper winding 10f relay 4W2, to The picking up of relay 4WZ with its polar contacts operated to a right hand position closes an obvious circuit at front contacts 56 and 51 for causing the operation. of the switch machine 48M to a normal position. Iffthe switch machine tSM is already in a normal position at the time relay 4WZ is picked up, the picking up of relay AWZ causes the dropping away of relay ILS to close the signal control circuit by opening its circuit at back contact 30, because the correspondence relay 4NCR remains picked up to hold open the stick circuit for relay 4LS at back contact 59.

If, however, switch machine ASM is in a reverse position prior to its energization for operation to a normal position, the picking up of relay 4BN opens the above described energized circuit for relay 4RCR to cause that relay to drop away and close back contact 58 in the stick circuit for relay 4L8 to cause relay 4L8 to be maintained picked up by the stick circuit heretofore described until the track switches 4TSA and GTSB have been operated to a normal and locked position. The locking of the track switches iTSA and 4TSB together with the switch machine lSM in a normal position causes the energization of relay 4WP with its polar contactsop-- back contact 59 to cause-that relay to drop away and close the signal control circuit.

When relay 4W2 is picked up for operating the switch machine 4SM to a normal position,

astick circuit is closed during the operation of the switch machineto provide that the switch machine. will complete its operation, from through'a circuit including backcontact 63 of relay GWP, front contact 64 of relay 4WZ, polar contact 65 of relay 4WZ in a right'hand position, and upper winding of relay '4WZ, to

Each of .the track switches has an auxiliary control means provided by a switch control lever SML which has a. normal center position, a normal operating position shown to the right (see Fig. 2) and a reverse operating position shown to the left. 7 1. a

It is provided that the lock relays L can be picked up only when the auxiliary switch control lever SML for that track switch is in a normal position. Such a mode of operation provides that the track switches can be operated only when the lockv relays have had an o-pportunity .to pick up .prior to the operation of the switch control lever SML from its normal center position. Thus it .is-provided that the operation of the lever SML to an operating position causes the operation of the track switches only "if 'those track switches can be positioned at the time the lever is operated. Such a means for preventing the "preconditioning of track switches is conveniently. called by those familiar,

with the .art lever lock equivalent.

An example of the pick-up circuits provided for the lock relays for each ofrthe track switches is shown in Fig. 2 in which relay 8L, for example, is picked (up only when the detector track section B is unoccupied by a train and lever ESML is'in its normal center position. The pick-up circuit isclosed under such conditions from through a circuit including front contact 24 of relay 8T, front contact 22! of relay SES, front contact 222 of relay .BWS, winding of relay 8L, and contact 68 .of lever 4SML in a normal centerposition, to

When lever ASML is operated to a right hand normal operating position, at a time when the above described normal conditions of the system exist, relays iAN 'and lBN are picked up when their center windings are energized. The operation of lever 4SML to a normal operating right hand position closes a circuit for relay '4AN from through a circuit including contact 69 of lever 4SMLfin a right hand position, center winding of relay 4AN, .and back contact "If! of relay 4R, to In a similar manner the closing of contact "I! in a right hand position effects theenergization of an obvious circuit for relay QBN. The picking up of relays GAN and ABN cause the energization of relay-4WZ and the operation of the-switch machine to a normal locked position in the same manner .as heretofore described when relay 4BN was assumed to be pickedup in setting up a route by operation of the control buttons for the entranceand exit points.

I If lever- 4SML is operated to a reverseoperating left hand position, when the above described normal-conditions of the systemi exist, relay GR is picked up when its obvious circuit is energized for :its center winding upon the closing of contact 69 of lever 4SML in a left hand reverse operating position. ,The picking switches has completed its operation in accordance with the positions required in setting up each proposed route, it has been pointed out that the relay LS associated with that track switch is dropped away to close the signal control circuits.

To consider an example of the signal control circuits provided for each of the signals in the track layout, assume the track switches 4TSA and 4TSB to have completed their operation to a locked reverse position in accordance with a route defined by an operator by the depression of an entrance button for signal 14 and an exit button for signal l1. When relay 4L8 has been dropped away, a circuit is closed for relay MG (see Fig. 35) from through a circuit including front contact 72 of relay I 'IXR, back contact I3 of relay ALS, back contact 14 of relay dNCR, front contact 15 of relay 4RCR, back contact 1B of relay 4NCR, back contact 11 of relay GLS, back contact 78 of relay MXR, front contact 19 of relay MNR, and winding of relay MG, to The picking up of relay MG applies energy at front contacts 80 and 8! to the search light signal mechanism of signal M to cause that signal to display a green clear indication.

The clearing of each signal causes the dropping away of its signal at stop repeater relay M, as, for example, the clearing of signal l5 causes the dropping away of relay ISM (see Fig. .2) when signal-at-stop contact 34 of signal [5 is opened.

Route and approach Zoc7cing.-Inasmuch as the route locking used in this embodiment of the present invention is similar to that typically shown in prior applications, the route locking relays have been shown only in block form in the present disclosure (see Fig. 2). It is to be understood that the circuits by which those route locking relays are controlled are provided as typically shown, for example, in the prior application of Langdon, Ser. No. 175,466, filed November 26, 1937. It is also to be understood that other forms of route locking can as well be used, and that, if approach locking is required in practice, the route 'and approach locking can be provided as shown, for example, in the patent to C. F. Stoltz, Patent No. 2,115,511, dated April 26, 1938.

It is believed, however, that, for an understanding of the present invention, it is sufficient to consider that the relays ES and WS are respectively east and west directional stick normally energized relays, dropped away for the portion of each route occupied by, and in advance of, each train, and are energized as the passing train leaves the track section with which they are associated.

It is obvious, with reference to Fig. 2 of the accompanying drawings, that whenever either of the route locking relaysassociated with the detector track section for a particular track switch, are dropped away, the lock relay L for that track section is dropped away to cause the electric locking of that track switch to become effective.

Restoration to normal.To consider how a signal can be restored to stop, and the parts of the sysem associated with the setting up of routesrestored to normal at the will of an operator, assume, for example, an operator to cause the restoration of a route set up as heretofore described from signal 14 to signal I! by pulling out button MNB.

When button MNB is pulled out, the stick circuit for relay MNR is opened at normally closed contact 35 of button MNB to cause that relay to drop away. The dropping away of relay MNR. causes the dropping away of signal control relay MG (see Fig. 3B) by opening the circuit for that relay at front contact I9, and the opening of front contacts 80 and 81 caused by the dropping away of relay 14G deenergizes the mechanism in signal M to cause that signal to be restored to the position to display a red stop indication.

The dropping away of relay MNR also causes the dropping away of relay I'IXR by opening the circuit for that relay at front contact 39. When relay IIXR is dropped away, the upper winding of relay 4R is deenerg'ized, due to the opening of front contact 41 of relay I'lXR. Inasmuch as the detector track section is unoccupied at that time, the center winding of relay 4R is deenergized, thus causing that relay to drop away.

A very similar mode of operation is effected upon passage of a train, the principal difference being that the stick circuit for relay MNR is automatically opened as soon as a train accepts the entering signal M, instead of being opened by the manual actuation of the entrance button MNB. To consider an example of such restoration upon passage of a train, assume a route to be set up in a manner which has been described from signal I4 to signal I1, and assume an approaching train to accept signal 14 and enter rack section 8.

When a train enters track section 8 and relay ST is dropped away, under such condtions, the stick circuit for relay MNR is opened at front contact 31 of relay 8T to cause relay MNR to drop away and cause the restoration to normal of the relays associated with the route set up including that entrance point, and the restoration of signal M to stop, all in the same manner as described above, except that the restoration of relay 4R to normal is delayed until the passing train has left track sections 8 and 9.

Interlock between conflicting rontes.In an entrance-exit type system there is no looking or restraint of the manual actuation of the control buttons; and although the route locking forming a part of the system prevents actual power operation of switches in a route under or ahead of a train, even though the switch control relays to change the position of these switches might be energized, it is considered desirable that the operator should not be able by any manipulation of the control buttons to cause energization of any switch control relay to set up a route in conflict with the one occupied by a train. Among other things, such'preconditioning ofa switch in an occupied route for operation to a different position, when the train leaves and this switch is unlocked, is considered to be undesirable because it usually affords little, if any, additional facility in the movement of traffic, and adds the hazard that a switch so preconditioned might be improperly operated at. some time under or ahead of a train in case of some failure of the route locking means, due to a momentary loss of track circuit shunt or the like. Accordingly, it is considered preferable to arrange the system so that a train must clear a route, with such sectional rear release features as may be expedient, before any manipulation-of the control buttons is effective to set up any conflicting route.

As previously explained, the energization of a switch control relay for a given position of a switch opens-the initiating circuits for all routes over that .switch in its other position; ..-and .consequently so long as this switch control relay is energized, the manipulation of control buttons for any conflicting route .is effective,xsince no operating. potential is supplied to the exit relays .for such routes. In order to maintain this same interlock between conflicting routes while a route is occupied by a train, as well as whenthis route is set up by the route establishing means, :provision is made in accordance with this invention to maintain the switch vcontrolrelay for each switch in an occupied route energized :until the train has passed out of the route, orzat least out of the detector track section forathat switch.

A typical example of such controlof theswitch control relays is shown inTig. 2 for the crossover l. The middle windings of the switch control relays 4AN, 4BN, and 4R for this crossover 4 are provided with stick circuits closed when the lock relays 8L and BLassociated with ,thiscrossover are deenergized. It is contemplated .that the lock relays .for the various switches,.such as the lock relays 8L and SL for the crossover l, will be controlled by route locking means, preferably with sectional rear release in accordance with regular practice and in the manner di closed more in detail .in our prior specification No. 477,671, so that the lock relays .for each switch in a route is deenergized'when the entrance signal clears andis maintained deenergized ahead of a train traversing the route until that train has passed out of the corresponding detector track section. Although the simple track layout shown in Fig. 2 does not include enough switches or crossovers to takeadvantage of the rear release features affordedby the use of directional stick relays in this "type of route locking, the way in whichthe lockrelays are intended to be controlled by such .directional .stick relays is illustrated in Fig. 2 for the crossover d; and from this example it can be, readily under stood how the desirediinterlock between conflicting routes is maintained with such facility of ,sectional rear release that the track layout'may afford.

As a typical example of the contemplated operation, assume that the switch controlrelay 4B, is energized to establish a route over 'the'crossover l in the reverse position fromnsignalx I4 to signal 11 in the manner above explained. When the signal It assumes its clear condition, the directional, stick .rclays 8E8 and.9ES.for eastbound train movement are automatically deenergized, opening at their .front contacts 221 and 27-33 the circuits for the lock relays 8L and BL respectively. This deenergization of "thelockrelay 8L closes a stick circuit for the switch. control relay AR which may be traced from (-1-), through the back contact of this relay 8L, front contact 86 of relay 43, back contact 81 of relay lAN, middle winding of relay AR, and back contact 38 of relay 4BN, to Similarly, the deenergization of the lock relay 9L closes another stick circuit for the relay 4R, which may be traced from through the back contact 89 of relay 9L, front'contact 90 of relay 4R,

back contact '8"! of relay middle "winding of relay tAN, and back contact 88 of relay IBN, to In this way the switch control relay for the position of each switch included in a route is held up by a stick circuit as soon as the signal clears for train movement into the route.

In the example assumed, when a train leaves the track section 8 and the signal M assumes its stop condition, the directional stick relays 8E8 and QES are maintained deenergized in accordance with the mode of operation characteristic of this form of route locking, thereby keeping the lock relays 8L and 9L deenergized and the switch control relay 4R energized, although the entrance of this train automatically restores the entrance relay HlNR in the. manner previously explained, thereby deenergizing'the exit relay I'IXR and the completion circuit for energizing the switch control relay 4R. "In this way, the switch control relays of switches in an cecupied route are kept energized to maintain the interlocking between conflicting routes after the route establishing means has been restored to normal.

In the case assumed, when the train leaves the track section 8 but is still in the track section 9, the lock relay 8L may pick up, but since both ends of the crossover 4 are assumed to be operated from the same switch machine, and the presence of a train in the track section 9 should prevent operation of this crossover, the switch control relay lR, is still held up by the lock relay 3L until the train also clears the track section 9. In the case of a more complicated track layout, however, where the rear release'of switches by the picking up of directional stick relays in the rear of a train is available, theenergization of a lock relay in this manner, and the resultant release of the associated switch control relay, can close initiating circuits for routes over a switch. in a difierent position before the train has entirely cleared the route.

If, in the example assumed, the train should move in the opposite direction over the route from signal I! to signal 14, the directional stick relays 8W8 and 9W8 for the other. direction are operated in the same manner to control the energization of relay 4R; and it can be seen that the control of the switch control relays in this manner acts to maintain the interlocking between coniiicting routes for both directions of trafilc.

End-to-end or through route'controL-To provide that an operator need only actuate the con-. trol buttons for the extreme ends of each route to be set up, irrespective of the number of intermediate signals included in that complete route, a system is provided whereby the route initiated is 'selected'by sections in a successive order, a section being provided for each interlocked group,

starting with the section for-the interlocked group nearest the exit point.

To'consider thegeneral mode of operation of the system in setting up routes by end-to-end control, assume, for example, an operator to initiate the setting up of a route from signal I6 tosignal l I, at a time when the normal conditions of the system exist as illustrated and heretofore described. v

In setting up a route from signal IS to signal I i, relay IGNR. (see Fig. IE) is picked up when the entrance button 'IBNB is depressed, and the picking up of relay lBNR. applies energy to the initiating network in such a manner as to feed toward closes a portion of the selecting network circuit for completing a'circuit through to the exit relay for each available exit point. Although the general mode of operation of the system is to pick up a route selector relay Y for each track switch 

